text: const { expectEvent, expectRevert } = require('@openzeppelin/test-helpers');
  
  const ERC1967Proxy = artifacts.require('ERC1967Proxy');
  const UUPSUpgradeableMock = artifacts.require('UUPSUpgradeableMock');
  const UUPSUpgradeableUnsafeMock = artifacts.require('UUPSUpgradeableUnsafeMock');
  const UUPSUpgradeableBrokenMock = artifacts.require('UUPSUpgradeableBrokenMock');
  const CountersImpl = artifacts.require('CountersImpl');
  const expect = require('chai').expect;
  
  contract('UUPSUpgradeable', function (accounts) {
    before(async function () {
      this.implInitial = await UUPSUpgradeableMock.new();
      this.implUpgradeOk = await UUPSUpgradeableMock.new();
      this.implUpgradeUnsafe = await UUPSUpgradeableUnsafeMock.new();
      this.implUpgradeBroken = await UUPSUpgradeableBrokenMock.new();
      this.implUpgradeNonUUPS = await CountersImpl.new();
    });
  
    beforeEach(async function () {
      const { address } = await ERC1967Proxy.new(this.implInitial.address, '0x');
      this.instance = await UUPSUpgradeableMock.at(address);
    });
  
    it('upgrade to upgradeable implementation', async function () {
      const { receipt } = await this.instance.upgradeTo(this.implUpgradeOk.address);
      expect(receipt.logs.filter(({ event }) => event === 'Upgraded').length).to.be.equal(1);
      expectEvent(receipt, 'Upgraded', { implementation: this.implUpgradeOk.address });
    });
  
    it('upgrade to upgradeable implementation with call', async function () {
      expect(await this.instance.current()).to.be.bignumber.equal('0');
  
      const { receipt } = await this.instance.upgradeToAndCall(
        this.implUpgradeOk.address,
        this.implUpgradeOk.contract.methods.increment().encodeABI(),
      );
      expect(receipt.logs.filter(({ event }) => event === 'Upgraded').length).to.be.equal(1);
      expectEvent(receipt, 'Upgraded', { implementation: this.implUpgradeOk.address });
  
      expect(await this.instance.current()).to.be.bignumber.equal('1');
    });
  
    it('upgrade to and unsafe upgradeable implementation', async function () {
      const { receipt } = await this.instance.upgradeTo(this.implUpgradeUnsafe.address);
      expectEvent(receipt, 'Upgraded', { implementation: this.implUpgradeUnsafe.address });
    });
  
    it('reject upgrade to broken upgradeable implementation', async function () {
      await expectRevert(
        this.instance.upgradeTo(this.implUpgradeBroken.address),
        'ERC1967Upgrade: upgrade breaks further upgrades',
      );
    });
  
    // delegate to a non existing upgradeTo function causes a low level revert
    it('reject upgrade to non uups implementation', async function () {
      await expectRevert(
        this.instance.upgradeTo(this.implUpgradeNonUUPS.address),
        'Address: low-level delegate call failed',
      );
    });
  
    it('reject proxy address as implementation', async function () {
      const { address } = await ERC1967Proxy.new(this.implInitial.address, '0x');
      const otherInstance = await UUPSUpgradeableMock.at(address);
  
      // infinite loop reverts when a nested call is out-of-gas
      await expectRevert(
        this.instance.upgradeTo(otherInstance.address),
        'Address: low-level delegate call failed',
      );
    });
  });
  